Global Authentication Incorporated has now given way to Global Authority. GAI was founded in California and graded cards, packs and autographs. After falling on some tough times not long ago, the company sold its card grading business to two former employees. There are many cards in GAI holders. They were generally regarded as quite 
reputable and accurate in the early years. Some collectors still swear by them.
GAI graded all types of cards, but primarily vintage cards. They were the first company to grade unopened packs and were still doing so at last check. PSA has assumed the larger role in that regard, however.
However, since PSA, SGC and Beckett have risen to the dominant role in the industry, many collectors have chosen to crack their cards out of Global holders and have them re-graded and re-holdered by those companies. Sometimes bargains can be had by spotting solid vintage graded GAI cards since not that many people are searching for them these days.
As of early 2012, Global Authority’s Facebook and Twitter pages were active, but dormant. Because of some of the uncertainty surrounding the company, GAI or Global graded cards can often be found at below market prices and are sometimes a good source for cheap baseball cards. Look for sellers who have an old stash they are moving. There are plenty of sellers, too. Over 2,000 cards graded by GAI are on eBay.